A Separation Agreement is a contract, and if the Agreement was valid and binding when signed, it will be valid and enforceable at a later date.
However, if you are looking to use an older Separation Agreement as part of a Divorce filing now, the document must fully and accurately reflect the financial condition of the parties today. If the document is not completely accurate with all assets and liabilities disclosed as of the date of filing the case, a new Separation Agreement may be required. (You should also check the local court where a divorce action is to be filed; that court may require, as part of their local rules, a more up to date agreement as part of the case.)
Details on the relevant legal forms software titles from Standard Legal:
Separation Agreement Legal Forms Software
No Fault Divorce (no Children) Legal Forms Software